Encouraging memory efficiency

[Timon Gehr via Digitalmars-d]

On 07/17/2014 06:27 PM, Tero wrote:
> Just watched Don's DConf 2014 talk where he said D has to be ruthless about
> memory inefficiency. Here's one thing that I think could help avoid
> unnecessary garbage: built-in syntax for this:
>
> import core.stdc.stdlib : alloca;
> ubyte[] buffer = (cast(ubyte*) alloca(bufsize)) [0 .. bufsize];
>
> Often bufsize is not known at compile-time but it won't change after the
> buffer
> allocation. So there's no reason to create garbage other than the
> *inconvenience*
> of using alloca. Allocating in the stack seems ideal so I'd encourage
> that by a
> clean syntax. I keep missing this feature.

Well, there is always this hack:

import core.stdc.stdlib : alloca;
auto createBuffer(T,alias size)(T[] 
buf=(cast(T*)alloca(size))[0..size]){ return buf; }

void main(){
     auto bufsize=5;
     auto buffer=createBuffer!(ubyte,bufsize);
     import std.stdio;
     writeln(buffer);
}